It is beneficial in oil and gas drilling to be able to transmit data collected downhole to a surface rig, and to be able to transfer data from the surface rig to a location that is downhole. For example, collecting navigation and other relevant downhole data and transmitting this data to the surface rig is a common practice. This practice is typically referred to as “Measurement-While-Drilling” (MWD). Logging data may also be transmitted uphole, and if so, this practice is referred to as Logging-While-Drilling (LWD). Signals may be transmitted bidirectionally; for example, control signals may be sent from the surface rig to MWD and LWD equipment that is located downhole.
Commercialized MWD and LWD technologies include mud pulse telemetry, in which pressure pulses are generated in and transported through drilling mud by periodically constricting the flow of the drilling mud through a drill string. However, data transmission rates available using mud pulse telemetry are relatively slow (<1 bit/second), which limits the type of data that can be usefully collected. Wireline telemetry has also been used, and it provides greater data throughput than mud pulse telemetry, but electric cables that are used to transmit data up and down the drill string are vulnerable to damage and impose limitations on the operation of the drill string.
Wireless telemetry technology other than mud pulse telemetry technology has been developed that avoids the physical limitations of wireline cables and has a higher data transmission rate than mud pulse telemetry. An example of wireless telemetry other than mud pulse telemetry is electromagnetic telemetry, in which signals are sent as electromagnetic waves through the earth. Electromagnetic telemetry is limited to operating in areas where formation resistivity is in an acceptable range that permits signal transmission.
Another type of wireless telemetry is acoustic telemetry, which involves transmitting data as acoustic waves via media such as drill pipe. Several technical challenges exist when attempting to communicate using acoustic telemetry; for example, when performing MWD or LWD using acoustic telemetry, one challenge is ensuring that an above-surface receiver receives acoustic waves of sufficient amplitude and quality.
Given the continued need for transmitting data collected downhole to a surface rig, and for transferring data from the surface rig to a location that is downhole, research and development accordingly continue into methods, systems, and techniques for transmitting data during drilling.